Sorry, then I misunderstood the request.

IMHO, Git only supports "Prune obsolete worktrees" which already exists as a menu item.

Please use "Use Message for Commit" and then the interactive rebase. It highlights equally named commits and offers auto-squash commands.

In the log window of version 19.1 there is a "Use Message for Commit" command.

Should it apply to the whole file or just for new characters?